Te amSetManager.php: permission denied

Hello ! I have a strange problem. Every once in a while I got the following messages.When it happens, SugarCRM Pro 7.2.1 almost freezes or is showing: "loading message" forever. When I look in the logs apache-errorlog I see:

I changed the rights on the folder /var/www/html a dozen times. Group/user is: apache:apacheI also made a chmod -R 777 for the entire folder. It works one or two days and then it reappears.The rights of the file /var/www/html/cache/modules/Teams/TeamSetCache.php changes to rw/rw/r-- (660). But why ? Why is SugarCRM doing this ? Apache itself is running under apache:apache as well.Any hints ?